Sub-Surface Equilibration of Hydrogen with the a-Si:H Network Under Film Growth Conditions

1993 ◽  
Vol 297 ◽  
Author(s):  
ILSIN An ◽  
Y.M. Li ◽  
C.R. Wronski ◽  
R. W. Collins
Keyword(s):  
Hydrogen Diffusion ◽  
Film Growth ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Emission Rates ◽  
Near Surface ◽  
Kinetic Information ◽  
Reaction Processes ◽  
Surface Conversion

In this study we characterize hydrogen diffusion and reaction processes in the near-surface (top 200 Å) of a-Si:H that lead to network equilibration under standard conditions of plasma-enhanced chemical vapor deposition (PECVD). Real time spectroscopic ellipsometry (SE) is used to provide continuous kinetic information on the near-surface conversion of Si-Si to Si-H bonds during exposure of in situ-prepared films at 250°C to filament-generated atomic H. We have found that for optimum PECVD a-Si:H, the formation of additional Si-H bonds is limited by the capture of H at trapping sites, and the rapid diffusion process (D>10-14 cm2/s) by which H reaches the site is not detected optically. Deep trapping occurs at a rate of ∼10 3 s-1 under our filament conditions, estimated to generate ∼1020 cm-3 mobile H in the near-surface of the film. Finally, more than 1021 cm-3 additional H atoms are trapped with emission rates <2×10-7 s-1, suggesting trap depths >2.0 eV. Shallower traps are also detected at lower concentration.

Growth of GaAs/AlGaAs Quantum Dots Using Self-Organized InP Stressors

1995 ◽  
Vol 417 ◽  
Author(s):  
M. C. Hanna ◽  
Z. H. Lu ◽  
A. F. Cahill ◽  
M. J. Heben ◽  
A. J. Nozik
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Organic Chemical ◽  
Near Surface ◽  
Self Organized ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

AbstractGaAs quantum dots were formed in a near surface quantum well (QW) by producing lateral confinement with self-organized InP stressors grown in situ by metal organic chemical vapor deposition (MOCVD). We report here the influence of growth conditions on InP island formation on AlGaAs/GaAs single QW structures and also the influence of the QW structure on the optical properties of the GaAs quantum dots. We observe strong photoluminscence up to room temperature from the strain-induced quantum dots with energy redshifts of 70 meV below the QW peak.

scholarly journals Carbon-Involved Near-Surface Evolution of Cobalt Catalyst during Reaction: An in-situ Study

2020 ◽  
Author(s):  
Feng Yang ◽  
Haofei Zhao ◽  
Wu Wang ◽  
Qidong Liu ◽  
Xu Liu ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Carbon Diffusion ◽  
Deposition Process ◽  
Catalytic Performance ◽  
Surface Evolution ◽  
Near Surface ◽  
Co Catalysts ◽  
Transmission Electron ◽  
Walled Carbon Nanotubes

Abstract When carbon-containing species are involved in reactions catalyzed by transition metals at high temperature, the diffusion of carbon on/in catalysts dramatically influence the catalytic performance. Acquiring information on the carbon-diffusion-involved evolution of catalysts at atomic level is crucial for understanding the reaction mechanism yet also challenging. For the chemical vapor deposition process of single-walled carbon nanotubes (SWCNTs), we developed methodologies to record in-situ the near-surface structural and chemical evolution of Co catalysts with carbon permeation using an aberration-corrected environmental transmission electron microscope and the synchrotron X-ray absorption spectroscopy. The nucleation and growth of SWCNTs were linked with the partial carbonization of catalysts and the alternating dissolvement-precipitation of carbon in catalysts. The dynamics of carbon atoms in catalysts brings deeper insight into the growth mechanism of SWCNTs and also sheds light on inferring mechanisms of more reactions. The methodologies developed here will find broad applications in studying catalytic and other processes.

Thin films for superconducting electronics: Precursor performance issues, deposition mechanisms, and superconducting phase formation-processing strategies in the growth of Tl2Ba2CaCu2O8 films by metal-organic chemical vapor deposition

1997 ◽  
Vol 12 (5) ◽  
pp. 1214-1236 ◽  
Author(s):  
Bruce J. Hinds ◽  
Richard J. McNeely ◽  
Daniel B. Studebaker ◽  
Tobin J. Marks ◽  
Timothy P. Hogan ◽  
...  
Keyword(s):  
Thin Films ◽  
Chemical Vapor Deposition ◽  
Vapor Pressure ◽  
Vapor Deposition ◽  
Film Growth ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Organic Chemical ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

Epitaxial Tl2Ba2CaCu2O8 thin films with excellent electrical transport characteristics are grown in a two-step process involving metal-organic chemical vapor deposition (MOCVD) of a BaCaCuO(F) thin film followed by a postanneal in the presence of Tl2O vapor. Vapor pressure characteristics of the recently developed liquid metal-organic precursors Ba(hfa)2 • mep (hfa = hexafluoroacetylacetonate, mep = methylethylpentaglyme), Ca(hfa)2 • tet (tet = tetraglyme), and the solid precursor Cu(dpm)2 (dpm = dipivaloylmethanate) are characterized by low pressure thermogravimetric analysis. Under typical film growth conditions, transport is shown to be diffusion limited. The transport rate of Ba(hfa)2 • mep is demonstrated to be stable for over 85 h at typical MOCVD temperatures (120 °C). In contrast, the vapor pressure stability of the commonly used Ba precursor, Ba(dpm)2, deteriorates rapidly at typical growth temperatures, and the decrease in vapor pressure is approximately exponential with a half-life of ∼9.4 h. These precursors are employed in a low pressure (5 Torr) horizontal, hot-wall, film growth reactor for growth of BaCaCuO(F) thin films on (110) LaAlO3 substrates. From the dependence of film deposition rate on substrate temperature and precursor partial pressure, the kinetics of deposition are shown to be mass-transport limited over the temperature range 350–650 °C at a 20 nm/min deposition rate. A ligand exchange process which yields volatile Cu(hfa)2 and Cu(hfa) (dpm) is also observed under film growth conditions. The MOCVD-derived BaCaCuO(F) films are postannealed in the presence of bulk Tl2Ba2CaCu2O8 at temperatures of 720–890 °C in flowing atmospheres ranging from 0–100% O2. The resulting Tl2Ba2CaCu2O8 films are shown to be epitaxial by x-ray diffraction and transmission electron microscopic (TEM) analysis with the c-axis normal to the substrate surface, with in-plane alignment, and with abrupt film-substrate interfaces. The best films exhibit a Tc = 105 K, transport-measured Jc= 1.2 × 105 A/cm2 at 77 K, and surface resistances as low as 0.4 mΩ (40 K, 10 GHz).

Morphology Optimization of Very Thick 4H-SiC Epitaxial Layers

2013 ◽  
Vol 740-742 ◽  
pp. 251-254
Author(s):  
Milan Yazdanfar ◽  
Pontus Stenberg ◽  
Ian D. Booker ◽  
Ivan.G Ivanov ◽  
Henrik Pedersen ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Epitaxial Growth ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Epitaxial Layers ◽  
Power Devices ◽  
Chemical Vapor Deposition Reactor ◽  
Thick Layers

Epitaxial growth of about 200 µm thick, low doped 4H-SiC layers grown on n-type 8° off-axis Si-face substrates at growth rates around 100 µm/h has been done in order to realize thick epitaxial layers with excellent morphology suitable for high power devices. The study was done in a hot wall chemical vapor deposition reactor without rotation. The growth of such thick layers required favorable pre-growth conditions and in-situ etch. The growth of 190 µm thick, low doped epitaxial layers with excellent morphology was possible when the C/Si ratio was below 0.9. A low C/Si ratio and a favorable in-situ etch are shown to be the key parameters to achieve 190 µm thick epitaxial layers with excellent morphology.

In Situ Heteroepitaxial Bi2Sr2CaCu2O8 Thin Films Prepared by Metalorganic Chemical Vapor Deposition

1993 ◽  
Vol 335 ◽  
Author(s):  
Frank Dimeo ◽  
Bruce W. Wessels ◽  
Deborah A. Neumayer ◽  
Tobin J. Marks ◽  
Jon L. Schindler ◽  
...  
Keyword(s):  
Thin Films ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Chemical Vapor ◽  
Oxide Phase ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
Metalorganic Chemical

AbstractBi2Sr2CaCu2O8 thin films have been prepared in situ by low pressure metalorganic chemical vapor deposition using fluorinated β–diketonate precursors. The influence of the growth conditions on the oxide phase stability and impurity phase formation was examined as well as the superconducting properties of the films. Thin films deposited on LaAIO3 substrates were epitaxial as confirmed by x-ray diffraction measurements, including θ-2θ and φ scans. Four probe resistivity measurements showed the films to be superconducting with a maximum Tc0 of 90 K without post annealing. This Tc0 is among the highest reported for thin films of the BSCCO (2212) phase, and approaches reported bulk values.

Rapid Thermal Low Pressure Metalorganic Chemical Vapor Deposition of InP and Related Materials

1993 ◽  
Vol 300 ◽  
Author(s):  
A. Katz ◽  
A. Feingold
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Low Temperatures ◽  
Metalorganic Chemical Vapor Deposition ◽  
Film Growth ◽  
Chemical Vapor ◽  
Hole Mobility ◽  
Low Pressure ◽  
Growth Conditions ◽  
Metalorganic Chemical

ABSTRACTHigh quality InP and In0.53Ga0.67As undoped and Zn-doped layers were grown by means of rapid thermal low pressure metalorganic chemical vapor deposition (RTLPMOCVD) technique, using tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBA), as the phosphorus and arsenic sources. The InP films were grown at a P:In ratios of about 75 and the InGaAs films were grown at a As:In ration of about 2, low temperatures at the range of 450-550°C, pressures it the range of 1-4 tons, and growth rates of 2-3 nm/sec. All the film growth conditions were optimized to yield defect-free layers with featureless morphology, which reflected at a minimum backscattering yield (Xmin) as low as 3.1% for the InP and 3.6% for the InGaAs. These films presented a good electrical properties, as well, with hole mobility of 4200 cm2/Vs for the undoped-InP layers and 75 cm2/Vs for the undoped-InGaAs layers.

Atomic-Scale Analysis of Plasma-Enhanced Chemical Vapor Deposition from SiH4/2 Plasmas on Si Substrates

1998 ◽  
Vol 507 ◽  
Author(s):  
Shyam Ramalingam ◽  
Dimitrios Maroudas ◽  
Eray S. Aydil
Keyword(s):  
Gas Phase ◽  
Surface Reaction ◽  
Film Growth ◽  
Chemical Vapor ◽  
Atomic Scale ◽  
Scale Analysis ◽  
Si Substrates ◽  
Stages Of Growth ◽  
Key Factor ◽  
Reaction Processes

ABSTRACTWe present a systematic atomic-scale analysis of the interactions of SiH3radicals originating in silane containing discharges with Si(001)-(2×1) and H-terminated Si(001)-(2×1) surfaces. Through simulations, we show that the hydrogen coverage of the surface is the key factor that controls both the surface reaction mechanism and the reaction probability. The SiH3radical reacts readily with the pristine Si(001)-(2×1) surface during the initial stages of growth while its reactivity with the corresponding H-terminated surface is considerably lower. Deposition of a-Si:H from SiH3 radicals has also been simulated by repeatedly impinging SiH3 radicals onto Si(001)-(2×1) surfaces maintained at 500 °C. During deposition under these conditions, the dominant mechanism of hydrogen removal from the surface is through abstraction by SiH3 radicals, which subsequently return to the gas phase as silane. The important reaction processes that take place during film growth have been identified and their energetics has been analyzed.

Characterization of Silicon-Nitride Film Growth by Remote Plasmaenhanced Chemical-Vapor Deposition (Rpecvd)

1993 ◽  
Vol 334 ◽  
Author(s):  
Zhong Lu ◽  
Yi Ma ◽  
Scott Habermehl ◽  
Gerry Lucovsky
Keyword(s):  
Gas Flow ◽  
Film Growth ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Nitride Film ◽  
Silicon Nitride Film ◽  
Flow Rates ◽  
Plasma Generation ◽  
Atom Source ◽  
Rate Ratios

AbstractWe have characterized RPECVD formation of Si-nitride films by relating the chemical bonding in the deposited films to the growth conditions. Gas flow rates for different N- and Si-atom source gases have been correlated with (i) the film stoichiometry, i.e., the Si/N ratio, and the (ii) the growth rate. N2 and NH3 were used as N-atom source gases, and were either delivered (i) up-stream through the plasmageneration tube, or (ii) down-stream. Different flow-rate ratios of NH3/SiH4 were found for deposition of stoichiometric Si-nitride films using up-stream or down-stream introduction of NH3. This is explained in terms of competition between excitation and recombination processes for the N-atom precursor species. Stoichiometric nitride films could not be obtained using the N2 source gas for (i) either up-stream or down-stream delivery, and (ii) for plasma powers up to 50 W. This is attributed to the higher relative binding energy of N-atoms in N2 compared to NH3, and to significant N-atom recombination at high N2 flow rates through the plasma generation region.

scholarly journals Thin film stress and microstructure analysis by energy-dispersive diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C724-C724
Author(s):  
Christoph Genzel
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Residual Stress ◽  
Film Growth ◽  
High Energy ◽  
Energy Dispersive ◽  
Film Stress ◽  
Ex Situ ◽  
Near Surface

The most important advantage of energy dispersive (ED) diffraction compared with angle dispersive methods is that the former provides complete diffraction patterns in fixed but arbitrarily selectable scattering directions. Furthermore, in experiments that are carried out in reflection geometry, the different photon energies E(hkl) of the diffraction lines in an ED diffraction pattern can be taken as an additional parameter to analyze depth gradients of structural properties in the materials near surface region. For data evaluation advantageous use can be made of whole pattern methods such as the Rietveld method, which allows for line profile analysis to study size and strain broadening [1] or for the refinement of models that describe the residual stress depth distribution [2]. Concerning polycrystalline thin films, the features of ED diffraction mentioned above can be applied to study residual stresses, texture and the microstructure either in ex-situ experiments or in-situ to monitor, for example, the chemical reaction pathway during film growth [3]. The main objective of this talk is to demonstrate that (contrary to a widespread opinion) high energy synchrotron radiation and thin film analysis may fit together. The corresponding experiments were performed on the materials science beamline EDDI at BESSY II which is one of the very few instruments worldwide that is especially dedicated to ED diffraction. On the basis of selected examples it will be shown that specially tailored experimental setups allow for residual stress depth profiling even in thin films and multilayer coatings as well as for fast in situ studies of film stress and microstructure evolution during film growth.

The mechanism of laser-assisted CVD of germanium

1989 ◽  
Vol 4 (3) ◽  
pp. 634-640 ◽  
Author(s):  
T. R. Gow ◽  
D. G. Coronell ◽  
R. I. Masel
Keyword(s):  
Growth Process ◽  
Film Growth ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Main Role ◽  
Appreciable Change ◽  
Silica Substrate ◽  
Arf Laser ◽  
Germanium Films

Previous workers have shown that germane does not decompose below 700 K on silica substrates. However, if the germane is irradiated with an ArF or KrF laser, germanium films will grow at temperatures down to 610 K. In the work reported here, the role of the laser in the growth process was explored. First, the species impinging on the substrate during ArF laser-assisted chemical vapor deposition (LCVD) were analyzed with a mass spectrometer. The analysis showed that when germane is irradiated with an ArF laser under growth conditions, digermane is formed in the gas phase. The digermane then impinges on the substrate and pyrolyses. Many other species have been reported previously to be formed transiently during the laser pulse. However, we were not able to detect any other species with a high enough flux onto the substrate to condense at an appreciable rate. Next, temperature programmed decomposition was used to see if photochemical decomposition of chemisorbed germane played an important role in film growth. It was found that a laser dose comparable to that needed for film growth did not produce an appreciable change in the decomposition spectra. Lastly, film growth studies were used to examine the role of the digermane formed by the laser in the film growth process. It was found that a mixture of germane and digermane will decompose on a silica substrate down to 580 K to produce a germanium film. The growth characteristics of the germane/digermane mixtures were virtually the same as those seen in LCVD. Thus, it appears that under the conditions used previously for LCVD, the main role of the ArF laser is to convert some of the germane source gas to digermane. It also has been found that under other conditions, one can grow germanium films down to at least 300 K via digermane photolysis.

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